refactor(notifications): questionId → conversationId across bubble, deep link routing, FCM handling
- ActiveThreadMonitor: activeQuestionId → activeConversationId, enter/leave use conversationId
- MessageBubbleController: IncomingMessageBubble uses conversationId, show/dismissFor updated
- PartnerNotificationManager: CHAT_MESSAGE routes to conversation, payload includes conversationId
- MessageBubbleOverlay: onOpen passes conversationId, pointerInput keys on conversationId
- AppMessagingService: chat_message type reads conversation_id, bubble show uses conversationId
- MainActivity: deepLinkRouteFromIntent reads conversation_id from FCM extras